(531e) Keynote Talk - Positive Power with Negative Emissions: Flexible Ngcc Enabled By Modular Direct Air Capture (DAC)

Natural gas power generation is a vital part of the U.S. energy system based on an abundant domestic energy source. In this talk a way to modify natural gas combined cycle (NGCC) plants such that they produce power with a negative carbon footprint will be described. To achieve this, we have integrated the natural gas combined cycle (NGCC) system with both conventional amine capture and direct air capture (DAC). This combination provides dispatchable operation of the combined system to deliver carbon negative electricity even when variable renewable energy (VRE) resources are scarce. During times of high VRE, the unit would reduce its electrical output and allocate more energy to the DAC system, removing more CO2 from the atmosphere driving the carbon footprint further negative. This requires manipulation of the DAC system operation to optimize steam use to enable maximum value to be derived from time varying pricing of electricity.

The NGCC plant will include conventional amine scrubbing to remove 97% of the CO₂ contained in the flue gas. The amount of DAC will depend on the balance of using steam from the heat recovery steam generation system to make power through the turbine system and its use for regenerating the DAC sorbent. The NGCC plant will also be able to ramp up and down maintaining a minimum load to allow for fast response to pricing signals. Overall this will allow for carbon negative electricity to be produced between 60-100% of the NGCC operating capacity with an additional penalty of 5-20% of the NGCC generating capacity, above that required for conventional capture, depending on how much steam is directed to the DAC plant.